In order to cure certain types of compositions, contact between a curable component contained in the composition and a catalyst is sometimes necessary. For example, in the case of a hydrosilylation reaction-curable organopolysiloxane composition, the curable component in the composition is crosslinked by a hydrosilylation reaction catalyst such as a platinum-based catalyst, but curing begins when the catalyst and the curable component come into contact, so it may be necessary to prevent the catalyst and the curable component from coming into contact with one another during storage, for example, until curing is required.
One mode for avoiding contact between the catalyst and the curable component is a so-called two-component composition, a first part of which contains the catalyst and a second part of which contains the curable component. However, two-component compositions have poor workability due to the need to mix the two components immediately before use, for example. Moreover, two-component compositions are complicated to handle and sometimes even require a complex device for mixing.
Therefore, so-called one-component compositions have been proposed in which the catalyst and the curable component are present in the same system. In a one-component composition, the catalyst is coated or micro-encapsulated to ensure that the catalyst and the curable component do not come into contact. For example, Japanese Unexamined Patent Application Publication Nos. S64-45468, S64-47442, S64-51140, H02-9440, H02-117960, H07-26147, H07-70442, H11-236508, 2006-002093 and WO2007/032481 disclose one-component curable organopolysiloxane compositions containing a platinum-based catalyst enclosed in a thermoplastic resin such as polyethylene, polystyrene, or a silicone polymer.
However, the present inventors discovered that such one-component curable organopolysiloxane compositions containing so-called encapsulated catalysts have problems in that the storage stability over time is insufficient and in that increases in the viscosity of the composition over time cannot be sufficiently avoided. For example, in a conventional one-component curable organopolysiloxane composition, it has been observed that the platinum-based catalyst and the polysiloxane component come into contact during storage and that changes occur over time due to a hydrosilylation reaction. The viscosity of the composition increases as a result, which causes the composition to cure.
Accordingly, an object of the present invention is to obtain an encapsulated catalyst with which a one-component curable organopolysiloxane composition can demonstrate better storage stability.
Another object of the present invention is to obtain a one-component curable organopolysiloxane composition which demonstrates favorable storage stability by avoiding increases in viscosity over time.